EDM mold havles

Hi,

I have a core and cavity for an injection mold milled with a tight parallel toolpath. I'm slightly concerned about how perfectly they will fit together (one half is still on the milling machine) given that the milling machine is fairly slow the stepover of the parallel is 0.1mm, so there will be some micro cusps.

We have an EDM machine and I am wondering if EDM'ing both halves together to get a perfect fit is something anyone does? of if there are any problems with this method? It seems like this should lead to a perfect mold without having to go crazy on the parallels stepovers.

any advice appriciated

I once read a old sparker manual for a hurco that mentioned this for curved shut outs, but I’ve never known anyone do it. Maybe it never caught on?

I also can’t remember what sort of settings it suggested as it wouldn’t be dissimilar materials?

It's VERY VERY Slow!!!! You have to keep changing polarity to get equal wear on both halves, the machine RAM has to have the capacity to "lift" one half, non-conductive alignment bushings, plenty of clean oil washing away all of the swarf, no "dry" spots, also, no pockets that might trap gas, and cause an explosion!! Probably 20 years since I've done it - like watching paint dry!! Hope this helps!!------------- John

I second jptech's comments.
I've done it and it wasn't worth it.
Slow like watching paint dry is a pretty optimistic way to describe it.

Also, as jptech points out, the ram needs to have lots of lifting capacity.
This was not a big problem back when sinker EDM's all had hydraulic rams.
Nowadays, you'll risk boogering the machine.

My old Hansvedt SM 150B (hydraulic ram) had over 300 lb ram capacity.
My newer servomotor driven Hansvedt Foreman has 25 lb ram capacity.
They're the same sized machines.

No way I can match burn anything but small mold inserts on the new machine.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

In the late 80s we would EDM spot smaller intricate molds. We would spin nylon bushings for core half. Even small machines have plenty of lift.

Thanks for bringing back these memories. I would say in 2019 it shouldn't be an option .

Mrjoesnow,

Burning Steel-To-Steel is rarely performed these days, but the Makino Sinker EDM's still have standard conditions for this! It's already been stated that this process is very SLOW, and while this is true, this method still might represent a viable solution to some people.

It was also mentioned to watch the amount of weight that is placed on the Z-Axis of the Sinker EDM machine, and this is an excellent point (thanks Marcus)! The max weight that can be placed on the Z-Axis will differ by machine make and model, but the Makino Sinker EDM's will support weights up to 165 pounds on the smaller machines (EDAF2/EDAF3), and from 220 lbs. up to 660 lbs. on the larger EDNC-Series machines depending on configuration.

The most common practice today is to perform High-Speed Milling on both mold halves and machine them to a negative stock to minimize hand fitting. The practicality of this requires proper techniques from the Milling Machine, Programming Methods, and Tooling/Cutters that are used, but this is the most efficient method used in the industry.

- Brian